Suppressed carrier modulator



Feb. 19, 1957 H. T. MORTIMER 2,782,376

SUPPRESSED CARRIER MODULATOR Filed Feb. 24, 1956 22 CAR RIER SOURCE FlLTER MODULATION SOURCE INVENTOR HAR RY T. MORTI M ER ATTORNEYS:

United States Patent SUPPRESSED CARRIER MODULATOR Harry T. Mortimer, LosAngeles, Calif.

Application February 24, 1956, Serial No. 567,694

9 Claims. (Cl. 33251) (Granted under Title 35, U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The invention relates in general to magnetic modulation means and inparticular to a modulation means for suppressed carrier operation.

Suppressed carrier operation, with which this invention is primarilyconcerned, is commonly employed where it is desirable to avoidunauthorized monitoring of the communication system. This type ofoperation involves the elimination of the carrier frequency from thetransmitter output when a zero modulation voltage is applied to thecarrier. Generally the carrier suppression is accomplished by complexelectronic circuitry. ample, as shown in the patent to Duncan No.1,560,505, is'suedNovember 3, 1925, a multi-phase source of carrierfrequency oscillations arranged for in-phase or outof-phase modulationwhereby signaling energy is impressed on the antenna only when themodulation is in-phase might be employed. It will be seen that asimplified suppressed carrier modulation system would be highlydesirable. Accordingly:

It is an object of this invention to provide a simple magneticmodulation means which permits suppressed carrier operation.

It is still another object of this invention to utilize a non-linearcharacteristic of grain oriented rolled steel in the modulation of acarrier frequency.

It is still another object of this invention to provide a fast actingmeans for intermittently mixing two frequencies to produce a sinusoidalproduct frequency.

Other objects of this invention will become apparent upon a morecomprehensive understanding of the invention for which reference is hadto the attached specification and drawings.

In the drawings:

Fig. 1 depicts one embodiment of this invention.

Fig. 2 is a graphical showing of the permeability characteristic ofgrain oriented material.

Fig. 3a and Fig. 3b are graphical showings of the hysteresis curves fora grain oriented material in the direction of grain orientation and inthe direction perpendicular to the grain orientation, respectively.

Briefly, the invention comprises a unique inductive field interactionbetween two coils which are wound in crosswise manner on a metallicform. One of the coils is energized at the carrier frequency and theother is energized at the modulation frequency. In a preferredembodiment the output is taken through a high pass filter connected inparallel with the coil being energized at the modulation frequency. Bywinding the two coils on a grain oriented material and introducing anadditional magneticfield the non-linear hysteresis characteristic ofthegrain oriented material is utilized as the essential non-linearcharacteristic in the frequency mixing process to produce a modulatedoutput. In the invention For ex- 2 ,782,376 Patented Feb. 19, 1957 iceboth coils must be energized for inductive interaction. In the preferredembodiment, there is no output when modulation ceasesin typicalsuppressed carrier fashion.

Referring now to the drawings:

Fig. 1 depicts a structural arrangement of one embodiment of theinvention wherein coil 10 and coil 20 are wound on metallic form 30 suchthat the axis of the coils are in orthogonally disposed relation.

A low frequency source 11 capable of producing, for example, a 2 kc.modulation signal is connected across the two terminals, 12 and 13, ofthe coil 10. A high frequency source 21 capable of producing, forexample, a 60 kc. carrier frequency is connected across the twoterminals, 22 and 23, of the coil 20. The output circuit comprises afilter 40 whose input terminals, 41 and 42, are connected acrossterminals 12 and 13, and whose output terminals, 43 and 44, areconnected across the output load 56. As will be seen, filter 40 isprovided merely to isolate the modulation source 11 from the output.Thus the only critical requirement of this filter in the embodiment ofFig. l is that it be capable of passing a band of frequencies in theregion of the carrier frequency.

An additional magnetic field producing means 60 is disposed in parallelrelation to the axis of the coil 20 to permit interaction between thefield produced by the energized coil 20 and that produced by theenergized means 6ft. As depicted in the drawings, means 60 may be a barmagnet, or alternatively, an electromagnetic means might be employed.

As is well known, the modulation of one frequency with another is aproduct sinusoidal function which requires a processing of the twosinusoidal waves through a non-linear medium. For example, in a balancedmodu later the non-linear gm characteristic of the tubes is utilized inthe processing of the sinusoidal waves by critically biasing the tubesin the non-linear region of the gm curve.

In the device of this invention the non-linear characteristic requiredin the processing of the sinusoidal waves is provided by saturablybiasing grain oriented material in one direction.

In more detailed explanation, a grain oriented material is employed asthe metallic form 30 on which the coils 10 and 20 are cross-wound. Thegrain oriented material utilized in this invention is normally producedby a cold rolling procedure on silicon iron, generally with a siliconcontent up to 3.5%. This manufacturing procedure provides a magneticallyanisotropic sheet in which the crystalline structure seems to take up apreferred orientation and the finished sheet has directional magneticproperties similar to those for a single crystal. As indicated in Fig.2, the direction of highest permeability is in the rolling direction.Likewise, as seen in Figs. 3a and 3b, the lowest hysteresis loss is alsoin the rolling direction. Such materials are commercially known asHypersil, Trancor 3x, etc.

in accordance with the invention, the coils l0 and 20 are so disposed onthe metallic form 30 that the magnetomotive force of coil 10 is in thedirection of grain orientation and the magnetomotive force of coil 20 isin a direction perpendicular thereto. In addition, a unidirectionalsource 60 is disposed to produce a magnetomotivc force in the same planeas that of the coil 29.

This additional magnetomotive force has the effect of partiallysaturating the magnetically anisotropic sheet in the directionperpendicular to the direction of grain orientation.

In simplified analysis, the anisotropy of the frame material affords amutual coupling between the two coils when both the carrier signal andthe modulation signal are present and the extent of this coupling is afunction of the non-linearity of the hysteresis loop of the magneticallyanisotropic material. With the addition of the magnetomotive force ofsource 60 the material is partially saturated in one direction causingthe carrier to operate in a non-symmetrical manner about the hysteresisloop. The resultant etfect is then the desired mixing of the carrierfrequency and the modulation to produce a modulated output.

Since the two coils, 10 and 20, are in orthogonal arrangement in thisinvention it will be seen that in the absence of either the carrier orthe modulation frequency, no inductive coupling between the coils 1t)and 20 is possible. As previously mentioned the output is taken acrossthe coil 10 in the embodiment shown. Thus, in the absence of themodulation signal, the carrier signal will not reach the input of filtercircuit 60 and there will be no carrier signal output.

The invention described herein provides a new and simplified carriersuppressed modulation system which does not employ vacuum tubes orcomplex circuitry and thus overcomes many of the inherent disadvantagesof prior known systems.

It is understood, of course, that the invention which has beenexemplarily described herein, may be readily employed in othermodulation systems wherein suppressed carrier operation is not requiredby taking the output across the terminals 22, 23 of coil 20. Finally, itis understood that the invention is to be limited only by the scope ofthe appended claims.

What is claimed is:

l. A magnetic modulation means comprising a first signal source forproducing a modulation frequency, a second signal source for producing acarrier frequency to be modulated, first and second coil windingsconnected to said first and second signal sources, respectively, saidfirst and second coil windings being wound in crosswise manner on a formof magnetically anisotropic material having a determined grainorientation such that the magnctomotive force of said first coil windingis in the direection of grain orientation of said material and themagnetomotive force of said second coil winding is in a directionperpendicular thereto, unidirectional magnetic means for producing amagnetomotive force in a direction perpendicular to the direction ofgrain orientation of said magnetically anisotropic material and in thesame plane as the magnetomotive force of said second coil winding, andfiltering means capable of passing frequencies in the region of saidsecond frequency source connected across said first coil winding forobtaining a modulated output signal therefrom.

2. A magnetic modulation means comprising a first signal source forproducing a modulation frequency, a second signal source for producing acarrier frequency to be modulated. first and second coil windingsconnected to said first and second signal sources, respectively, saidfirst and second coil windings being wound in crosswise manner on a formof magnetically anisotropic material having a determined grain oforientation such that the magnetornotive force of said first coilwinding is in the direction of grain orientation of said material andthe magnetomotive force of said second coil winding i in a directionperpendicular thereto, permanent magnet means for producing amagnetomotive force in a direction perpendicular to the direction ofgrain orientation of said magnetically anisotropic material and in thesame plane as the magnetomtive force of said second coil winding. andfiltering means capable of passing frequencies in the region of saidsecond frequency source connected across said first coil winding forobtaining a modulated output signal therefrom.

3. A magnetic modulation means comprising a first signal source forproducing a modulation frequency, a

' second signal source for producing a carrier frequency to bemodulated, first and second coil windings connected to said first andsecond signal sources, respectively, said first and second coil windingsbeing wound in crosswise manner on a form of magnetically anisotropicmaterial having a determined grain orientation such that themagnetomotive force of said first coil Winding is in the direction ofgrain orientation of said material and the magnetomotive force of saidsecond coil winding is in a direction perpendicular thereto,unidirectional magnetic means for producing a magnetomotive force in adirection perpendicular to the direction of grain orientation of saidmagnetically anisotropic material and in the same plane as themagnetomotive force of said second coil winding, and high pass filtermeans connected across said first winding for obtaining a modulatedoutput signal therefrom.

4. A magnetic modulation means comprising a first signal source forproducing a modulation frequency, a second signal source for producing acarrier frequency to be modulated, first and second coil windingsconnected to said first and second signal sources, respectively, saidfirst and second coil windings being wound in crosswise manner on a formof magnetically anisotropic material having a determined grainorientation such that the magnetomotive force of one of said coilwindings is in the direction of grain orientation of said material andthe magnetomotive force of the other of said coil windings is in adirection perpendicular thereto, unidirectional mag netic means forproducing a magnetomotive force in the same direction and plane as themagnetomotive force of the coil winding connected to said second signalsource, and filtering means capable of passing frequencies in the regionof said second frequency source connected across one of said coilwindings for obtaining a modulated output signal therefrom.

5. A magnetic modulation means comprising a first signal source forproducing a modulation frequency, a second signal source for producing acarrier frequency to be modulated, first and second coil windingsconnected to said first and second signal sources, respectively, saidfirst and second coil windings being wound in crosswise manner on a formof magnetically anisotropic material having a determined grainorientation such that the magnetomotive force of one of said coilwindings is in the direction of grain orientation of said material andthe magnetomotive force of the other of said coil windings is in adirection perpendicular thereto, unidirectional magnetic means forproducing a magnetomotive force in the same direction and plane as themagnetomotive force of the coil winding connected to said second signalsource, and filtering means capable of passing frequencies in the regionof said second frequency source connected across the coil windingconnected to said first signal source for obtaining a modulated outputsignal.

6. A magnetic modulation means comprising a first signal source forproducing a first frequency; a second sig nal source for producing asecond frequency to be modulated with said first frequency; first andsecond coil windings connected to said first and second signal sources,respectively; said first and second coil windings being wound incrosswise manner on a form of magnetically anisotropic material having adetermined grain orientation such that the magnetomotive force of saidfirst coil winding is in the direction of grain orientation of saidmaterial and the magnetomotive force of said second coil Winding is in adirection perpendicular thereto, uni-directional magnetic means forproducing a magnetomotive force in a direction perpendicular to thedirection of grain orientation of said magnetically anisotropic materialand in the same plane as the magnetomotive force of said second coilwinding; and output means connected across said first coil winding forobtaining an output signal therefrom; said output means including asignal rejection means capable of rejecting said first frequency.

7. A magnetic modulation means comprising a first signal source forproducing a first frequency; a second signal source for producing asecond frequency to be modulated With said first frequency; first andsecond coil windings connected to said first and second signal sources,respectively; said first and second coil windings being wound incrosswise manner on a form of magnetically anisotropic material having adetermined grain orientation such that the magnetomotive force of saidfirst coil winding is in the direction of grain orientation of saidmaterial and the magnetomotive force of said second coil winding is in adirection perpendicular thereto; permanent magnet means for producing amagnetomotive force in a direction perpendicular to the direction ofgrain orientation of said magnetically anisotropic material and in thesame plane as the magnetomotive force of said second coil winding; andoutput means connected across said first coil winding for obtaining anoutput signal therefrom; said output means including a signal rejectionmeans capable of rejecting said first frequency.

8. A magnetic modulation means comprising a first signal source forproducing a first frequency; a second signal source for producing asecond frequency to be modulated with said first frequency; first andsecond coil windings connected to said first and second signal sources,respectively; said first and second coil windings being wound incrosswise manner on a form of magnetically anisotropic material having adetermined grain orientation such that the magnetomotive force of saidfirst coil winding is in the direction of grain orientation of saidmaterial and the magnetomotive force of said second coil winding is in adirection perpendicular thereto; unidirectional magnetic means forproducing a magnetomotive force in a direction perpendicular to thedirection of grain orientation of said magnetically anisotropic materialand in the same plane as the magnetomotive force of said second coilwinding; and output means connected across one of said coil windings forobtaining an output signal therefrom; said output means including asignal rejection means capable of rejecting the output frequency of thesignal source connected in parallel with said output means.

9. A magnetic modulation means comprising a first signal source forproducing a first frequency, a second signal source for producing asecond frequency to be modulated with said first frequency; first andsecond coil windings connected to said first and second signal sources,respec tively; said first and second coil windings being wound incrosswise manner on a form of magnetically anisotropic material having adetermined grain orientation such that the magnetomotive force of saidfirst coil Winding is in the direction of grain orientation of saidmaterial and the magnetomotive force of said second coil winding is in adirection perpendicular thereto; permanent magnet means for producing amagnetomotive force in a direction perpendicular to the direction ofgrain orientation of said magnetically anisotropic material and in thesame plane as the magnetomotive force of said second coil winding, andoutput means connected across one of said coil windings for obtaining anoutput signal therefrom, said output means including a signal rejectionmeans capable of rejecting the output frequency of the signal sourceconnected in parallel with said output means.

References Cited in the file of this patent UNITED STATES PATENTS

